Bi-directional magnetic domain transfer circuit

ABSTRACT

This invention relates to the transfer of single-wall magnetic domains between two independent circuits identified as a major loop and a minor loop. The invention discloses the use of two separate magnetic elements in the linking portion of the transfer circuit with a common current conductor.

United States Patent [191 Flannery July 22, 1975 Bl-DIRECTIONAL MAGNETIC DOMAIN 3,713,116 1/1973 Bonyhard et a1 340/174 TF TRANSFER CIRCUIT l/l973 Kish et a]. 340/174 TF [75'] Inventor: William E. Flannery, Norristown,

Primary Examiner-Stanley M. Urynowicz, Jr. [73] Assignee: Sperry Rand Corporation, Blue Bell, Attorney Agent or Firm-Rene Kuypers [22] Filed: Nov. 9, 1973 ABSTRACT [21] App]. No.: 407,675 7 This invention relates to the transfer of single-wall i magnetic domains between two independent circuits identified as a major loop and a minor loop. The ini vention discloses the use of two separate magnetic ele- [58] Fleld of Search 340/174 174 SR ments in the linking portion of the transfer circuit with References Cited 21 common current conductor.

UNITED STATES PATENTS 6 Claims, 4 Drawing Figures 3,697,963 lO/l972 Kish et a]. 340/174 TF C D a E MINOR LOOPS T-T *1 I READ V V L- .l V DA A OUT T l6 l4 l2 L MAJOR LOOP PATENTEDJUI 22 I975 896,421

SIEEI 1 MINOR LOOPS r- 7- 1 l l n m l l A READ V V V DATA OUT IN I4 \MAJOR LOOP VERTICAL COMPONENT CONDUCTOR OF CONDUCTOR FIELD 18 BARRIER H l! 1III I-I +II LPE FILM T Ias BUBBLE FIELD PATENTEDJUL 22 ms SHEET CONDUCTOR BI-DIRECTIONAL MAGNETIC DOMAIN TRANSFER CIRCUIT BACKGROUND OF THE INVENTION U.S. Pat. No. 3,714,639 and all patents cited therein are made of record in this patent application.

The transfer arrangement disclosed in U.S. Pat. No. 3.7 l4,639 is considered to have shortcomings chief of which is the requirement to provide insulation in the transfer circuit between the metal loop conductor and a contiguously positioned magnetically soft dollar sign shaped element, which is located in the transfer region. This insulation requirement is required since the dollar sign shaped guide element would cause the metal loop to short circuit if there were no insulation between them. Obviously, without insulation the sys- SUMMARY OF THE INVENTION The instant invention provides for a facile arrange ment whereby data in a data processing arrangement may readily be transferred from its major loop to its minor loop.

The present invention is based on the utilization of a metal conductor overlay which is directly positioned over two separate and distinctive magnetic elements in a magnetic domain transfer circuit. This direct contact arrangement is made possible by the fact that the metal conductor overlay is in contact with the respective magnetic elements at only one location so that there is no possibility of an electrical short circuit of the conductor by means of the current carrying magnetic circuit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 depicts the overall data processing arrangement which utilizes the instant invention.

FIG. 2 is the circuit arrangement which is utilized for bi-direction transfer of information between major and minor loops of a data processing system.

FIGS. 3a and 3b represent sectional views to illustrate the operation of the field gradient.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, there is shown an overall arrangement of a mass memory organization 10 which utilizes the instant invention. The mass memory 10 in a preferred embodiment is formed on a thin single crystal orthoferrite or garnet wafer or deposited film. When the film is fabricated it is deposited so that the easy vaxis is perpendicular to the surface of the wafer. The

wafer is then subjected to an external magnetic bias field H n, perpendicular to its surface. The bias field acts to stabilize closed wall domain in the film as closed wall cylindrical domains, The absence or presence of a domain represents for data processing purposes a binary O or 1.

In general, the mass memory organization 10 incorporates a major binary information loop 12 wherein data circulates around the loop in a serial fashion. In other words, the loop represents and endless track or shift register wherein binary data circulates. Data enters the major loop 12 at the DATA IN or generator position and circulates in the endless shift register. The major loop has a sensor station 16 for reading out information from the major loop if it is required.

For purposes of explanation, the major loop 12 may at a certain location and time show the presence of the binary data 11011. The I data is represented in FIG. 1 by the domains present in the major loop 12 beside the minor loops A, B, D and E; the 0 data is represented by the absence of a domain opposite minor loop C. It is required in mass memory organization to transfer a word or byte between the major loop 12 to facilitate data storage in the minor loops and data manipulation in the major loop. The data may represent, for example, fixed data such as the sine of an angle, or the calculation of a progamming sub-routine which is to be temporarily stored in the minor loops. Therefore, it is necessary to be able both to readily enter data from the major loop 12 to the minor loops A, B, C, D and E, and vice versa. 1

The instant invention is directed in particular to the area enclosed by the dotted outline which encompasses a portion of both the major loop and the minor loop and the discussion following will be generally limited to this area. Accordingly for purposes of simplicity, the transfer of a magnetic domain (i.e., binary in the major loop 12 to the minor loop D will only be discussed. The transfer of the remaining information, it should be understood, will be transferred in a similar manner. I

Reference is now made to FIG. 2 and the operation and construction of the bi-directional magnetic domain transfer circuit. The figure shows a layout of a portion of the major loop 12 made up of a plurality of soft magnetic Ts A, C, and F and soft magnetic bars, B and G. The minor loop D is composed of the magnetic elements I, J and H. The soft magnetic Y elements E and D provide the linking elements between major loop 12 and the minor loop D. The T, Y and bar pattern in the major and the minor loops are fabricated by providing a thin film Permalloy overlay on the wafer 10.

A metal conductor overlay, B, is positioned over the Permalloy pattern to provide a field gradient that together with an in-plane magnetic field, H permits the transfer of domains from the major to the minor loops. The current carrying conductor, B, is a metal conductor such as gold which is electro deposited on the wafer and the Permalloy overlay pattern. It should be particularly noted in the arrangement of the conductor B with respect to the Permalloy pattern that it does not touch the linking Y or other Permalloy elements at more than one location. This is significant in that a short circuit cannot occur across the metal conductor B by means of the Permalloy pattern, which is a current carrying element. The importance of this fact is that in the fabrication of the gold conductor it can be directly placed over the overlay pattern without an insulating separator. Y

Let us assume now that a magnetic domain or binary l is to be transferred from the major loop 12 to the minor loop D. Normally field access domain propogation utilizing a counterclockwise rotating magnetic field H which is in the plane of the wafer is employed. The field acting in conjunction with the pattern of soft magnetic T and vertical bars causes the propogation of magnetic domains from right to left as seen in the drawing. The propogation of the magnetic domains proceeds from elements A, B, C, D, E, F and G when there is information transferred in the major loop only.

It should be understood that elements to G are only a portion of the major loop. The transfer is generally accomplished in the following manner.

The in-plane rotating H-field is provided by two orthogonal coils (not shown) that are driven by equal magnitude sinusoidal currents in phase quadrature. This causes the in-plane H-field to rotate through 360 and in the embodiment under discussion operates in the counterclockwise direction.

Assume that a magnetic domain is located in the major loop 12 at position 4 of the T-A. The numbers on the overlay represent locations whereat positive poles are produced when the rotating magnetic field vector reaches the compass position shown on the upper left hand side of FIG. 2. As the H-field rotates in the counterclockwise direction and reaches the vector position 1 on the compass, the magnetic polarity at location 1 of the T-A becomes In other words, the H- field causes free poles to be formed at the junction of the T such that location 1 is Assuming the convention that the domain is a magnetic charge, it can be readily understood that the domain moves from location 4 to location 1. When the H-field vector reaches position 2 on the compass, location 2 of T element B is charged and the domain transfers thereto. As the rotating field proceeds between 2 and 3 on the compass, the domain moves from location 2 to location 3 on bar-B. When the rotating field reaches vector positions 4, I and 2 in succession, location 4, 1 and 2 of the T-C become charged and the magnetic domain continues movement in the leftward direction ending up at location 2.

As the in-plane H-field continues its counterclockwise rotation, location 3- on the Y element D becomes between compass locations 2 and 3. This may be seen by normalizing the lower section of the Y element D to approximate a rectangular section. The charged domain therefore moves from location 2 on T element C to location 3- on Y element D. In a similar manner, location 3+ on Y-bar E becomes positive as the vector field moves between 3 and 4 so that the domain travels from 3- to 3+. The domain moves from locations 3 to 3+ since location 3+ is more strongly than location 3-. From thence the domain continues to move in a right to left direction from location 4, 1, and 2 of T element F to location 3 of vertical bar G.

It can be readily appreciated from the above description how a magnetic domain travels along a major loop utilizing a soft magnetic overlay pattern in conjunction with a rotating in-plane I-I-field.

Let us now assume a condition as seen in FIG. 1 wherein data such as l 101 1 represented by either the presence or absence of magnetic domains is to be transferred to the minor loops A to E. The description following will demonstrate how a single binary one bit located in the major loop 12 may be transferred to the minor loop D. It should be understood that this binary transfer is exemplary and would apply equally to the reached the direction which coincided with the leg of Y the Y element D for the location 3, the domain moved from location 2 on T element C to location 3 on Y element D. At this point in time, the domain on 1 bit was still circulating in the major loop. When it is determined to move a bit from the major to the minor loop a current pulse 1, producing a field H, is applied during the time period when the vectoris between locations 3- and 4. It will be recalled that in the discussion of domain transfer in the major loop only, transfer occurred in this same time frame.

The vertical component of the field H (see FIG. 3a) resulting from the current I, in conductor [5 gives rise to a field gradient which opposes domain motion across the width of the conductor. It is well known that a closed wall domain moves in a field gradient from regions of high bias field to low bias field. The field gradient (FIG. 3b) so caused by the current, 1,, acts to nullify the field gradient at position 3+ (see FIG. 2) on Y element E caused by the stray field from the magnetic poles at position 3+ when element E is magnetized by the rotating field H The'resulting field gradient at position 3+ on Y element E is such that it is substantially zero or negative going. This gradient is produced by summing the magnetic field forces H which is in a downward direction and H,, which is in an upward direction on the right side of conductor ,8 and downward directed on the left side as recognized by the application of Amperes Rule (FIG. 3b). However, in order for the domain to move, it must experience some portion of a positive field gradient. Since the field experienced by the domain is substantially zero it does not move from location 3- to 3+. In other words, movement in the major loop is terminated as the result of the application of the current 1,.

As the in-plane H-field continues to rotate it reaches the compass position 4 so that poles are formed thereat which can be seen by the normalizing of this rectangular section. At the same time, location 3 becomes less positively charged so that the negatively charged domain is influenced to move to location 4 of Y element D. The current pulse 1, is terminated just prior to the rotating field vector reaching location 4 on the Y element D. The continued rotation of the vector field causes the domain to continue movement to location 1+.

Upon further rotation of the I-I-field, location 2 on bar J has poles formed thereat and the domain moves from location 1+ to 2. At this point in time, the

, domain has been transferred into the minor loop D by cause of the formation of positive poles at location 3-. This can be also readily seen by normalizing this lower portion of the H bar. The domain moves from location 3- to 4 as the rotating vector rotates to the compass position 4 thereby inducing poles thereat. There is domain movement from location 3- to 4 since location 4 is more strongly positive than location 3. By further rotation of the H-field positive poles are induced in location 1 and negative poles in the vicinity of location 4 thereby causing a movement from 4 to 1.

This domain movement in the minor loop will continue in an upward direction (not shown) by locating similar H elements and bar elements in juxtaposition to one another. Eventually the domain will return via the H element shown and will be momentarily situated in locations 1, 2, and 3+ of the H-bar, location 4 of the l-bar and location I- in the Y-bar E.

Let us assume that the data processing system now requires that information should be transferred from the minor loop back into the major loop. This transfer takes place via the linking Y-bar E in the following manner.

After the domain is positioned at location 1- ofY element E, the current l is applied to conductor B. Consequently, the field gradient produced at location 1+ is substantially zero. As was previously discussed, this field gradient prevents movement from location 1 to location 1+. The current pulse I, is terminated just prior to the rotating field vector reaching location 2 of the Y-bar E. The action of the conductor current I accordingly prevents further domain motion in the minor loop.

The domain is therefore transferred along the linking element E by the in-plane field rotation from locations l-, 2 and 3+ and thence proceeds into the major loop along locations 4, 1 and 2 ofT element F and location 3 of bar G via normal field access propogation.

Although the preferred embodiment of the instant invention has been described such that at least two legs of the Y-shaped linking elements are equal in length, it should be understood that hose skilled in the art may vary this arrangement without departing from the spirit of this invention. Accordingly, in some cases it may be advantageous to utilize Y-shaped linking element wherein three legs thereof are all of differing lengths.

What is claimed is:

1. In a magnetic arrangementfor transferring a single-wall domain in a layer of magnetic material from a first closed-loop to a second closed-loop both defined by magnetically soft elements and utilizing an in-plane rotating magnetic field, the improvement comprising:

a. first and second identical, separate linking means arranged between said first and second closed loops and in a directly facing relationship,

b. a single conductor means positioned directly upon and for forming a magnetic gradient along said linking means,

said single conductor being oriented upward and downward repetitively between said first and second closed loops, said conductor being in contact with the elements of said first and second loops and said first linking means when oriented in an upward direction, said conductor being in contact with the elements of said first and second loops and said second linking means when oriented in a downward direction,

said first linking means providing means for transferring a wall domain from said first closed-loop to said second closed-loop, and said second linking means providing means for transferring said wall domain from said second closed-loop to said first closed-loop by rotating said in-plane field in conjunction with a timed current signal applied to said conductor. t

2. The magnetic arrangement in accordance with claim 1 wherein each said first and second linking means is substantially Y-shaped having two legs which are of greater length than its third leg.

3. The magnetic arrangement in accordance with claim 2 wherein said Y-shaped linking means are arranged so that the obtuse angle provided by said two greater length legs are facing one another with a slight offset.

4. The magnetic arrangement in accordance with claim 2 wherein said conductor means is positioned over one said greater length leg of said first Y-shaped linking means as well as over the greater length leg of said second Y-shaped linking means.

5. The magnetic arrangement in accordance with claim 1 wherein a current signal of a single direction is applied to said conductor for transferring said wall domain from said first closed loop to said second closed loop and vice versa.

6. The method of transferring a single-wall domain in a layer of magnetic material from a first closed-loop to a second closed-loop both defined by magnetically soft elements, and wherein first and second Y-shaped linking means are interposed between said loops, each respectively having two legs whose length is greater than the third leg, and a single transfer conductor positioned over one said greater length leg of said second Y- shaped means and utilizing the steps of:

a. applying a current to said transfer conductor in combination with an in-plane magnetic field to cause said domain to move from said first closedloop to said second closed-loop and vice versa.

b. timing the occurrence of the current signal in said transfer conductor during the period when the rotating magnetic field vector is between the obtuse angle formed between one said greater length leg and said short leg of the first Y-shaped means when a domain is being transferred from said first closed loop to said second closed loop, and

c. timing the occurrence of the current signal in said transfer conductor during the period when the rotating magnetic field vector is between the obtuse angle formed between one said greater length legs and said short leg of the second Y-shaped means when a domain is being transferred from said second closed loop to said first closed loop. 

1. In a magnetic arrangement for transferring a single-wall domain in a layer of magnetic material from a first closed-loop to a second closed-loop both defined by magnetically soft elements and utilizing an in-plane rotating magnetic field, the improvement comprising: a. first and second identical, separate linking means arranged between said first and second closed loops and in a directly facing relationship, b. a single conductor means positioned directly upon and for forming a magnetic gradient along said linking means, said single conductor being oriented upward and downward repetitively between said first and second closed loops, said conductor being in contact with the elements of said first and second loops and said first linking means when oriented in an upward direction, said conductor being in contact with the elements of said first and second loops and said second linking means when oriented in a downward direction, said first linking means providing means for transferring a wall domain from said first closed-loop to said second closed-loop, and said second linking means providing means for transferring said wall domain from said second closed-loop to said first closed-loop by rotating said in-plane field in conjunction with a timed current signal applied to said conductor.
 2. The magnetic arrangement in accordance with claim 1 wherein each said first and second linking means is substantially Y-shaped having two legs which are of greater length than its third leg.
 3. The magnetic arrangement in accordance with claim 2 wherein said Y-shaped linking means are arranged so that the obtuse angle provided by said two greater length legs are facing one another with a slight off-set.
 4. The magnetic arrangement in accordance with claim 2 wherein said conductor means is positioned over one said greater length leg of said first Y-shaped linking means as well as over the greater length leg of said second Y-shaped linking means.
 5. The magnetic arrangement in accordance with claim 1 wherein a current signal of a single direction is applied to said conductor for transferring said wall domain from said first closed loop to said second closed loop and vice versa.
 6. The method of transferring a single-wall domain in a layer of magnetic material from a first closed-loop to a second closed-loop both defined by magnetically soft elements, and wherein first and second Y-shaped linking means are interposed between said loops, each respectively having two legs whose length is greater than the third leg, and a single transfer conductor positioned over one said greater length leg of said second Y-shaped means and utilizing the steps of: a. appLying a current to said transfer conductor in combination with an in-plane magnetic field to cause said domain to move from said first closed-loop to said second closed-loop and vice versa. b. timing the occurrence of the current signal in said transfer conductor during the period when the rotating magnetic field vector is between the obtuse angle formed between one said greater length leg and said short leg of the first Y-shaped means when a domain is being transferred from said first closed loop to said second closed loop, and timing the occurrence of the current signal in said transfer conductor during the period when the rotating magnetic field vector is between the obtuse angle formed between one said greater length legs and said short leg of the second Y-shaped means when a domain is being transferred from said second closed loop to said first closed loop. 